National Jointed Goatgrass Research Program

 

Progress Report-2002

NOTICE
The following is a progress report containing preliminary data and results that may be modified by future research.
Please contact the listed authors
or Extension Coordinator for additional information.

 

1. TITLE: Effect of Controlling Jointed Goatgrass in Wheat Rotations in Nebraska in 2002

2. PERSONNEL: Gail A. Wicks, Gordon E. Hanson, and Gary W. Mahnken, University of Nebraska, 461 West University Drive, North Platte, NE 69101.

3. TIME LINE: Initiated 1996 to be completed 2003. We are on time.

4. ORIGINAL HYPOTHESIS: Jointed goatgrass (JGG) could be controlled using best weed and crop management practices used in winter wheat rotations.

5. SUMMARY OF PROGRESS: Initially in 1996, we overseeded with 200 JGG spiklets/m2 across all plots in 15 acres of a non-uniform JGG infestation. The three rotations, winter wheat-fallow (W-F), winter wheat-ecofallow corn-fallow (W-C-F, and winter wheat-ecofallow corn-corn-fallow (W-C-C-F) have been in place 6 years. After 6 years of data collection, the effects of crop rotations, winter wheat cultivars, and time of tillage are affecting JGG densities. Preventing weed growth after wheat harvest with herbicides and beginning tillage for fallow and corn production in April provided conditions suitable for more JGG seed germination before wheat planting than no-till in the wheat or corn stubble. This trend has been consistent. Wheat yields were equal between tillage and no-till except 1998 and 2002. In1998, JGG reduced yields 6 bu/A, but in 2002 no-till wheat yielded 4 bu/A more than wheat grown in a tilled seedbed. Tillage did not reduce corn yields following the ecofallow period in 1998 and 1999 because of timely rainfall, but yields were less than no-till in 1997, 2000, and 2001. In 2002, corn yields were zero because of drought.


In 2001, corn suffered from drought during the spring months. This reduced corn yields because of less crop residues needed to increase soil water storage and reduce evaporation. Corn was 5 inches taller when planted into Pronghorn, a medium-tall cultivar, winter wheat stubble than Vista, a short wheat, stubble. Winter wheat yields were also reduced by drought. JGG plant density in the winter wheat at harvest was 10 to 14 times greater in the winter wheat-fallow (W-F) than W-C-C-F or W-C-F rotations. Hail May 31 reduced wheat yields to 15 bu/A. Over the years the trend has been that the medium-tall Pronghorn wheat is more competitive with JGG than the two shorter cultivars.
In 2002, we experienced the driest year on record (since 1907) on the dryland farm. No JGG germinated in the wheat since the wheat was seeded in September 2001. Spring JGG germination was low, but fall rains greatly increased JGG emergence. Although several hundred JGG seedlings were killed in the fallow portion of the W-F rotation before wheat seeding, sufficient seeds germinated following a xx inch rain after wheat seeding September xx.
Few differences among winter wheat cultivars existed in 2002. Corn height was greater with corn planted into Pronghorn stubble than Vista wheat stubble. Corn height was shortest when corn followed corn.

6. OBJECTIVE: To determine the influence of best integrated weed management practices for controlling jointed goatgrass in winter wheat rotations. We are attempting to follow similar practices used by farmers using ecofallow.

7. EXPERIMENTAL DESIGN: Four replications of three rotations involving winter wheat-fallow, winter wheat-ecofallow corn-fallow, and winter wheat-ecofallow corn-corn-fallow were initiated in 1996. Pronghorn, Alliance, and Vista represent a medium-tall, medium, and short stature winter wheat cultivars adapted to western Nebraska were planted each year in the fallow plots. Two tillage treatments were imposed on each cultivar during the fallow and corn phases. One, tillage was used to plant the JGG in the spring during the fallow period before seeding winter wheat or corn. The other tillage treatment was no-till. Half of the corn plots were tilled with a mulch treader in April and cultivated in June. The other half of the corn plots was no-till. Herbicides were used to control weeds as needed during the fallow period following winter wheat harvest. All plots were treated with herbicides before tillage was performed. This eliminated weed control as a factor. Each rotational phase is present each year.

8. PROGRESS/CONCLUSIONS: The only difference among winter wheat cultivars existed in 2002 was height and test weight (Tables 1, 2). Pronghorn height was 3 inches taller than Alliance and 5 inches taller than Vista. Pronghorn test weight was greater than for Alliance and Vista. However, it still would be wise to plant taller cultivars in fields that are infested with jointed goatgrass. In addition, corn height was greater with corn planted into Pronghorn stubble than Vista wheat stubble.
Fall JGG counts in the fallow portion of the W-F rotation were extremely large as JGG density 914 plants/m2 in the tilled plots and 1020 plants/m2 were present. In the corn portion (corn stubble) of the W-C-F rotation, 58 JGG seedlings/m2 emerged in the tilled portion vs. 703 JGG seedlings/m2 in the no-till plots and 0 seedlings/m2 in the W-C-C-F rotation. Plants in the W-F rotation were killed with glyphosate before seeding wheat. Following wheat emergence 216 JGG plants/m2 were present in the tilled plots and 900 plants/m2 in the no-till that was tilled once before seeding. This large amount of JGG seedlings is related to a hail May 31, 2001 that destroyed the wheat canopy and allowed for high JGG seed production. Wheat yields will be greatly reduced in 2003 in the F-W rotation, while there should be little affect on the 2004 wheat crop in the F-W-C rotation as these plants were treated with glyphosate. Plus more will be killed during the upcoming fallow year. The JGG densities were greater in the fallow portion of the spring in the W-F rotation (15 JGG/m2) vs. 0 JGG/m2 in the W-C-F or W-C-C-F rotation (Table 3). Adding one or two summer crops following wheat allows sufficient time to reduce viable JGG seed density to an amount that would not affect winter wheat yield in a dry year or an area that has less rainfall than North Platte. To date, JGG has not greatly reduced wheat grain yields in any of the rotations. However, this will not be true in the 2003 wheat crop. Corn height was shortest when corn followed corn. Wheat yield was also less when following two corn crops. No-till increased wheat yields 4 bu/A.

Beginning tillage in early spring provided conditions suitable for more JGG seeds to germinate before wheat planting. In 2002, delayed rainfall caused insufficient JGG seeds to germinate before wheat seeding in the W-F rotation (Table 3). The high JGG density is related to a hail storm May 31, 2001 which destroyed the wheat canopy and allowed for high JGG seed production. This should have little affect on the 2003 wheat crop as these plants were treated with glyphosate. In farmers W-F fields that are hailed consider killing the wheat and jointed goatgrass with glyphosate to stop seed production. Otherwise crop management strategies must be changed to prevent yield loss in the next wheat crop.

9. PUBLICATIONS: One paper has been published. Wicks, G.A., G.E. Hanson, G.W. Mahnken, and S. D. Miller. 2001. Progress report on controlling jointed goatgrass in winter wheat in Nebraska with rotations. WWSS 54:67-71. A copy is available on the Web Site.

10. TECHNOLOGY TRANSFER ACTIVITIES: This program now has collected sufficient data for Technology Transfers. We now can follow JGG density changes throughout a rotation. Several wheat growers in southwest Nebraska have switched from winter wheat-fallow rotation to a three-year rotation to control JGG. Corn is the principle crop used following winter wheat in an ecofallow program. Growers using W-F had greater problems with JGG this fall. A field day in June 2002 was cancelled because drought. Another field day is planned for 2003. We revised our NebGUIDE on jointed goatgrass based on recent research
 

Table 1. Main-effect treatment means for JGG joint density, biomass, heads, and joint production before wheat harvest and winter wheat height and yield in 2002 at North Platte, NE.a

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                         Jointed goatgrass                                      Winter wheat     

             Plants     Biomass         Heads            Joints              Height   Test wt     Yield

_____________________________________________________________________________

Crop Rotation b           no./m2       kg/ha              no./m2              no./m2              inches     lb/bu        bu/A

 

C-C-F-W                      0             0.02                0                    0                    26.4 c     57.4 b     36.7 b       

W-C-F-W                     0             0.02               0                    0                    27.5 b     57.7 b      44.8 a

F-W-F-W                     0.02        0                    0                    0                    28.5 a     59.1 a      46.5 a

LSD (0.05)                   ns           ns                  ns                  ns                   0.9            0.5        2.9         

 

Tillage timing before harvesting wheat in 2002

Tillage (05-01-02)          0             0.2                 0                    0                    27           57.5 b      40 b

No-tillage                      0.01        0                    0                    0                    28           58.7 a      45 a

LSD (0.05)                   ns          ns                  ns                  ns                   ns             0.42        2

 

Cultivar

Pronghorn                     0.02        0                    0                    0                    30 a        59.3 a      43 a

Alliance                        0             0.02               0                    0                    27 b        58.1 b      44 a

Vista                            0             0                    0                    0                    25 c        56.8 c      42 a                 

LSD (0.05)                   ns           ns                  ns                  ns                   0.9            0.4        ns          

_____________________________________________________________________________

a JGG spikelets (200/m2) were seeded September 4, 1996.

b W = winter wheat, C = corn, F = fallow.

  

Table 2. Wheat variety effect means for jointed goatgrass density in spring and at fall harvest, and crop yield, North Platte, NE, 2002.a

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             Jointed goatgrass plants                                                          Crop yield                                                                               

                         Spring 2002 (April 5)         Fall 2002 (Sep. 19)

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Rotation b       Prongc   Alli       Vista         Prong         Alli       Vista              Prong       Alli       Vista

__________________________________    __________________________________________

--------------- no./m2 -------------         --------------- no./m2 -------------            ------ Height, inches -----

In corn

F-W-C            0          0             0             0.2           1.7          0.6               38 a        36 abc     36 ab      

F-W-C-C         1.0          0.9          1.4          426         395          320               34 bcd     33 cd      33 d

C-F-W-C         0.1          0.2          0.03           0             0             0                29 e        28 e        28 e

Mean               0.4          0.4          0.5          142         132         107               34 x      32 x       32 x

 

In wheat                                                                                                              bu/A

W-F-We          0.2            0             0             1.5          1.4        2.0                46 a        47 a        46 a

C-F-W               0          0.2            0                0          0.03         0                45 a        46 a        43 a

C-C-F-W        0.4          0.2          0.1                0             0          0                37 b        38 b        36 b

Mean              0.2          0.13        0.03        0.5 x          0.5 x     0.7 x              43 x        44 x        42 x

 

In fallow

F-W-F f              5.8          8.2          8.9          843 a       1050 a     1004 a           

W-C-F            0.4          1.7          0.8              0 b            0 b          0 b

W-C-C-F        2.7          3.5          6.3              0.05 b        0 b          0 b

Mean              2.9          4.4          5.3          281 x         350 x      335 x ____________________________________________________________________________

a Numbers followed by the same letter within rows and columns in blocks are not significant at the 0.05 level.

b W = winter wheat, C = corn, F = fallow. The first letter indicates the crop or fallow sequence in 2002.  

c Wheat cultivars: Prong = Pronghorn, Alli = Alliance, Vista = Vista.

d This is the corn phase, because of drought corn heights were measure July 16. 

e This is the wheat phase so grain yields are wheat. JGG counts are in wheat or corn stubble in spring and seedlings in wheat or corn in the fall.

f   This is the fallow phase, no grain yields.

 

Table 3. Effect of post-wheat harvest weed management in ecofallow on jointed goatgrass density in spring and fall and crop yield, North Platte, NE, 2002.a

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       Jointed goatgrass plants                                            Crop yield             

Spring 2002                Fall 2002

_____________________________________________________________________________

Rotation b       Tillage     No-till             Tillage     No-till                    Tillage     No-till

____________________________________________________________________________

       ------ no./m2 --------------                   --------no./m2 --------                               Height, inches

In corn

F-W-C c              2.2          0.02               60 b        720 a                     32 c        35 b

F-W-C-C         0.02         0.2                  0 c            0  c                    28 d        29 d

C-F-W-C           0             0                 0.02 c        1.6 c                    34 b        40 a

Mean              0.7          0.1                 19 y        234 x                      31 y        34 x

 

In wheat                                                                                                               wheat                                                                                                      bu/A

F-W-F-Wd            0          0.04                 0.1            3.2 a                   46 a        47 a

W-C-F-W          0             0                      0            0.02 b                 42 b        48 a

C-C-F-W           0             0                      0            0.03 b                 38 c        40 b

Mean             0 x          0.1x                 0.03 y        1.16 x                40 y        45 x

 

In fallow

W-F-W-F e     15.1        0.1               914 a      1017 a             

F-W-C-F          0           1.9                   0 b           0 b

W-C-C-F          0           8.3                   0 b            0.03 b

Mean             5.0         3.4                 72 y        299 x

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a Numbers followed by the same letter within rows and columns in blocks are not significant at the 0.05 level.

b W = winter wheat, C = corn, F = fallow. The last letter indicates the crop or fallow sequence in 2002. All plots were treated with atrazine + glyphosate after wheat harvest. Tillage occurred on half of the corn and fallow plots in April.  

c This is the corn phase, because of drought corn heights were measured July 16 which was the maximum height for the F-W-C-C rotation. Corn tasseled in the no-till plots in other rotations.

d This is the wheat phase so grain yields are wheat. Wheat cultivars: Prong = Pronghorn, Alli = Alliance, Vista = Vista.

e This is the fallow phase, no grain yields. JGG counts are in wheat or corn stubble in spring and seedlings in wheat or corn in the fall.

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